Llansadwrn (//; Welsh: [ɬanˈsadʊn]; Welsh pronunciation) is a small village in the community of Cwm Cadnant in south-east Anglesey, in north-west Wales. It lies between Menai Bridge, Pentraeth and Beaumaris. It is named after the church, founded in the 6th century by Saint Saturninus, who together with his wife, is commemorated by an early Christian monument.
St Sadwrn's Church is a Grade II*-listed building.
Close to the village was the site of the excavations that revealed the existence of Bryn Eryr Iron Age farmstead.
Andrew Crombie Ramsay (31 January 1814 – 9 December 1891) was a famous Scottish geologist. He died at Beaumaris in Anglesey and is buried at St Sadwrn's church, Llansadwrn where a glacial erratic boulder marks his grave.
- "Church of St Sadwrn, Cwm Cadnant". British Listed Buildings. Retrieved 12 January 2014.
- Right from the start: The Memoirs of Sir Wyn Roberts Archived 2006-02-08 at the Wayback Machine
- "Bryn Eryr Iron Age Farmstead". Museum of Wales. Retrieved 10 September 2017.
- Perkins, Donald. "Where is Llansadwrn?". llansadwrn-wx.info. Retrieved 21 December 2020.
V. E. Nash-Williams, The Early Christian Monuments of Wales, Cardiff, 1950 .